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Asthma

• Definition of Asthma
• Description of Asthma
• Causes and Risk Factors of Asthma
• Symptoms of Asthma
• Diagnosis of Asthma
• Treatment of Asthma
• What Questions To Ask Your Doctor About Asthma

Definition of Asthma

Asthma is a chronic inflammatory disorder of the airways within the lungs that affects over 17 million people in the United States.

Description of Asthma

The lung is the main organ of the respiratory system and its main function is respiration (exchange of gases between the environment and the body). Air enters the nose where it is filtered, warmed and humidified. After passing through the trachea (windpipe), the air travels into the lungs through the bronchi (a system of branching airway tubes that become smaller as they reach deeper into the lung). The smallest of the bronchi, the bronchioles, open into balloon-like sacs called alveoli.

An asthma attack occurs when these airways narrow and the muscles around them tightly contract (this is called bronchospasm). The membranes lining the inner walls of the airways become swollen and inflamed, and the glands within these walls produce excess mucus.

An asthma attack can be brief or it can last for several days.

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Causes and Risk Factors of Asthma

The two main factors that contribute to asthma are inflammation of the airway passages and hyperreactive bronchi.

When triggered by stimulus (see examples below), certain cells lining the airways release chemical substances called mediators that lead to inflammation. This inflammation causes the airway passages to swell, the cells lining the passages to produce excess mucus, and the airway opening to narrow.

Hyperreactivity means that when the bronchi are exposed to stimulus they respond in an exaggerated way by constricting the airway muscle and making it difficult to breathe.

The stimulus or "triggers" that can induce an asthma attack are:

• allergens (substances to which people are allergic), such as pollens, foods, dust, mold, feathers or animal dander
• irritants in the air, such as dirt, cigarette smoke, gases and air pollution
• odors in the household, such as household cleaners, perfumes, paints, varnishes, fabric softeners, laundry detergents and cooking fumes
• irritants in the workplace, such as fumes and vapors from wood products and metals
• metabisulfite - a food preservative found in dried fruits, fruit juices, beer, wine, salad bars and vegetables
• respiratory infections, such as colds, flu, sore throat and bronchitis
• too much exertion
• emotional stress, such as excessive fear or excitement
• weather conditions - very cold, windy or sudden changes in the weather
• medications, such as aspirin or related drugs, as well as some drugs used to treat glaucoma and high blood pressure
• menstrual cycle - Women with asthma occasionally have increased symptoms just before their menstrual period.
• nighttime - Asthma often worsens at night for a few reasons. The body releases chemicals during the night that may alter lung function. Also, the body's temperature tends to drop at night, which causes the airways to cool. Lastly, an exposure to allergens during the day takes up to several hours to affect the body. When the body reacts, it usually coincides with the nighttime hours.

Symptoms of Asthma

Airway inflammation and resulting narrowing air passages lead to the following symptoms of asthma:

• wheezing
• cough - chronic or recurring (worse particularly at night and in the early hours of the morning)
• pain or a tight feeling in the chest
• shortness of breath
• flaring of the nostrils when breathing in (especially in children)
• interrupted talking
• agitation
• hyperinflation (appearance of hunched shoulders, hunching forward or preferring not to lie down)

Diagnosis of Asthma

Asthma is sometimes hard to diagnose, because it can resemble other respiratory problems such as emphysema, bronchitis and lower respiratory infection. Therefore, the diagnosis of asthma is based on:

Spirometers and peak flow meters are used to measure how efficiently the patient can force air out of the lungs. Spirometers record the rate at which a person exhales air from the lungs and the total volume exhaled. Peak flow is a measurement of the fastest rate at which a person can force air out the lungs. The patient inhales and exhales into a small hand held device called a peak flow meter. A simple scale on the meter registers a value for peak flow. This reading helps the doctor evaluate current lung function. Laboratory tests may include blood and allergy tests.

Treatment of Asthma

Asthma cannot be cured, but it can be controlled with proper asthma management.

The first step in asthma management is environmental control. Asthmatics cannot escape the environment, but through some changes, they can control its impact on their health.

Listed below are some ways to change the environment in order to lessen the chance of an asthma attack:

• Clean the house at least once a week and wear a mask while doing it.
• Avoid pets with fur or feathers.
• Wash the bedding (sheets, pillow cases, mattress pads) weekly and in hot water.
• Encase the mattress, pillows and box springs in dust-proof covers.
• Replace bedding made of down, kapok or foam rubber with synthetic materials.
• Consider replacing upholstered furniture with leather or vinyl.
• Consider replacing carpeting with hardwood floors or tile.
• Use the air conditioner.
• Keep the humidity in the house low.

The second step is to monitor lung function. Asthmatics use a peak flow meter to gauge their lung function. Lung function decreases before the symptoms of an asthma attack - usually about two to three days prior. If the meter indicates the peak flow is down by 20 percent or more from your usual best effort, an asthma attack is on the way.

The third step in managing asthma involves the use of medications. There are two major groups of medications used in controlling asthma - anti-inflammatories (corticosteroids) and bronchodilators.

Anti-inflammatories reduce the number of inflammatory cells in the airways and prevent blood vessels from leaking fluid into the airway tissues. By reducing inflammation, they reduce the spontaneous spasm of the airway muscle. Anti-inflammatories are used as a preventive measure to lessen the risk of acute asthma attacks.

Corticosteroids are given in two ways - inhaled via a metered dose inhaler (MDI) or orally via pill/tablet or liquid form. Please note: Metered-dose inhalers are in the process of changing from the type propelled by liquified chlorofluorocarbons (CFCs) to a new, CFC-free delivery system (see the National Heart Lung and Blood Institute review on the new MDIs at http://www.nhlbi.nih.gov/health/public/lung/asthma/mdi.htm)

Bronchodilators work by increasing the diameter of the air passages and easing the flow of gases to and from the lungs. They come in two basic forms - short-acting and long-acting.

Advair is a newer inhaled medication that combines fluticasone and salmeterol to reduce both inflammation and airway constriction.

For more information on these medications, please see the Asthma Treatment report.

Some people cannot control the symptoms by avoiding the triggers or using medication. For these people, immunotherapy (allergy shots) may help. Immunotherapy involves the injection of allergen extracts to "desensitize" the person. The treatment begins with injections of a solution of allergen given one to five times a week, with the strength gradually increasing.

Note: Asthmatics vary considerably in their responses to different types, combinations and amounts of medicines so therapy must be carefully tailored to the individual. Even medication that may work well with some asthmatics may not be effective for others. Please discuss your individual situation with your doctor and both of you will determine a course of management that is best for you.

What Questions To Ask Your Doctor About Asthma

How can I best determine what will trigger my asthma?

What medication will you prescribe? What are the side effects?

During an attack, what measures (other than medications) can help relieve symptoms?

At what point are my symptoms severe enough so that I should come to your office or go to the Emergency Room?

Will I have an action plan based on my symptoms, home peak flow monitoring, or both?